Means for preventing the formation of scale in steam-boilers



F. I. DU PONT.

MEANS FOR'PREVENTING THE FORMATION` 0F SCALE IN STEAM BOILERS.

APPLICATION FILED MAY 3l, 1918.

MTA/Ess;

FRANCES I. :DU PGNT, 0E'

WILMINGTON, DELAWARE, ASSIGNOR-TO DELAWARE CHEMICAL ENGENEERING CMANY, Ofi' WILMINGTON, DELAWARE, A COR? POBATION 0F DELAWARE.

Y MEANS FOR PREVENTING THE FORMATION OF SCALE IN STEAM-BOILERS.

intenses.

To aZZ whom t may concern.' Be it known that l, FRANCIS l. DU PONT, a citizen of the United lStates, residing at lWilmington, county of New Castle, and State of Delaware, have invented a new and useful lmprovement in Means for Preventing the Formation of Scale in Steam-Boilers, ,of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, which form a part of this specification.

The object of my invention is to automatically maintain a constant level of water in a steam boiler and deliver feed water there- Y comprises means to pump water from ar water reservoir or tank to the boiler, means to return water from the boiler to the tank at a rate exceeding, or at least not less than, the rate at which the water is pumped to the boiler, a heat interchanger arranged to transfer heat from the water flowing away from the boiler to the water flowing toward the boiler to prevent the waste of heat that would otherwise occur, and means to prevent the Y conversion into steam of the water flowing from the boiler so as to insure the exchange of the maximum amount of hea-t before the return of the water to the tank.

The present invention embodies preferentially the same yfeatures of construction eX- ceptthat the feed pump, instead` of pumping water from the reservoir into which empties the overflow from the boiler, receives its supply from a source of fresh water, while the overflow from the boiler passes to a waste pipe. The present invention also contemplates the operation of the water-supply and water-discharge means at a rate of speed which will allow considerable excess to overflow, whereby the water in the boiler will Application led May 31,

changer prevents the uneconomical loss of heat which would.

, terchanger, Y operating mechanism. Only those parts and Specification of Letters Patent. Patentd Dec, 27, 1921,

.1918. Serial No. 237,450.

never become. suiciently concentrated to form scale, or will, even in the case of water of such quality that the formation of some scale is unavoidable, reduce the same to a minimum. By this arrangement the water 1n the boiler may be maintained almostas pure as fresh water, while the heat interdisadvantageous and otherwise occur.

A preferred embodiment of the invention is shown in the accompanying drawing, the single figure of which is a diagrammatic view of the steam boiler,

measuring engine and other codetails are shown which are essential to a full disclosure of the invention.

a represents the steam boiler; Z1 the desired Water level therein; c a pipe leading from any source of fresh water; and al the feed pump, which takes water from vthe pipe c and delivers it through the heat interchanger e into the boiler.

measuring engine (hereinafter vdescribed) is operated synchronously with the feedr pump cZ by any suitable means. I have shown the plungers of the engine and pum connected Aby a walking beam f pivoted between its ends to the frame of a steam engine. The reciprocating piston of the steam cylinder is shown connected to the plunger of the feed pump al, while the plungerh in the cylinder g of the measuring engine is connected to the fly wheel y of the steam engine by means of a connecting rod a.

The cylinder g of the measuring engine has at least as great a capacity as, and preferably a greater capacity than, the cylinder of `feed pump (Z. It has ports and a slide valve z' which is operated by a rigid arm j on the end of the plunger itself. rlhis arm Y j engages, just before the end of the inward stroke, with a shoulder h on the valve stem and shifts the valve to open communication between a pipe m (which leads from within the boiler at a point at which it is desired to maintain the water level) and the cylinder g of the measuring engine. J ust before the end of the outward stroke of the plunger h of the measuring engine, the rigid Varm y' engages a head Z on the end. of the valve stem and shifts the valve z' to close communication between the pipe ym and the cylinder g of the feed pump, heat inmeasuringY engine, at the same time opening communication between the cylinder g and the pipe n which leads to the heat interchanger.

As long asthe water level in the boiler a Vis above the end of the pipe the Vcylinder g, being of greater capacity than the cylin-Y der of the feed pump d, will take more water y Y "outof thev boiler than the feed pump can de- Veo liver into it. Vl/Vhen, however, the level of the water in the boiler falls below the end of the `pipe m, the latter willV receive only steam,

and the water level in the boiler will rise until equilibrium is established.

The heat interchanger e is not a substitute for the usual feed waterheater operating by exhaust steam from the engine. Should `an ordinary heater ybe used it must be introducedinl the pipe 0 between theI feed pump yand the heat inte1`^changer-V ,The purposeof the interchanger is toneutrali'ze what would Y otherwise be a waste of heat resulting from a continuousl withdrawal of hot water from the boiler.`

The heatV interchanger can'be of `any of the-well known formsybut that shown consists in a coil p for the feed water -extending through a chamber in which is a series of diaphragme v', each perforated with a small hplc, thus dividing the interchanger.

into a series of superimposed chambers, `the upper one of which contains the hottest into steam andcscape through the drain or waste pipe g. Under these conditions, very little of the heat would bey saved by the interchanger.

To obviate this l provide a differential valve s working in a valve casing interposed between the linterchanger and the drain pipe g. The lower chamber Yu of the valve casing connects with the lower chamber of the interchanger e and has a seat for theV head of the valve s which, when seated closes the lower chamberu 'from a middle chamber t connecting withthe drain. The

stem ofvalve s slides in a reduced' upperV end of the yvalve casing, the space above the stem forming the uppery valve chamber fu, which is connected by a pipe fw withY the steam space of the boiler a. The live steam pressure 1acting through the pipey fw? tends to hold valve s down on its seat, thereby changer.

closing the outlet fromYV the heaty interchanger. However, the lower end of the valve is larger in area than the end acted yon bythe live steam; and when Ythe pressure in the interchanger rises sufficiently, it raises the valve, and water from vthe .mterchanger escapesthrough chambers u and t into they drain pipe g. Thus, valves acts as ay regulating check `valve,.allowing exit of the VwaterV from thewinterchanger at a pressure which will vary with the boiler pressure, but will' be lowerin proportion A Aasthe area of thevseat is larger than thearea of the plunger ofthe valve.

*From the foregoing description Awill be understood that water will vbe supplied by y the feed pump ata rate 'in excessof that required to replenish water in the boiler that 'is'converted into steam and that this excess 'of vwater will be continuously withdrawn Vfrom the "boiler into Y *the interchanger,

`wherein the Vheat yof thevdischarged water will be abstracted by the water flowing from the feed pump tothe boiler; the temperature of the water discharginginto the drain being thereby Yreduced almost to the temper ature of the water flowing into the interl changer from the feed' pump.

`Three important ladvantages* are thereby secured. The feed water is deliverd to the boiler in a highly heated condition; the level of thewater in the boilerismairr tained; and the water in theboiler is con-V stantly being replenished with fresh water,

whereby the formation ofy scale is minlmized or altogether avoided. i

Having now fully described lmy invention, what l claim and desire to" protect by Letters Patent is: Y

' l. ln a feed water supply system for steam generators, a water feed line including Va pump for continuously'supplying fa predetermined amount yof fresh water to the generator, an overflow line including a measuring engine forjcontmuously removing the excess water supplied to the generator, a double 'surface heat interchanger connected to said line, theV ingoing Vwater pass-V ing over oneV surface nwhile 'the""outgoing water passes over theothe'r surface, to trans* fer the heat from the outgoing water to the ingoing wateigandmeans for controlling the discharge of vwater from the heat inter 2. ln a fee'clwater supply system for steam generators, a water feed line including a pum for continuously supplying a predetermined amount offresh water to the generator, an overflowvline including a measuring engine for continuously removing the excess lwater supplied to the generator, a double surface :heat interchanger connected tosaid lines, the 'ingoing water pass- 'ring over one Yisurf'af'zeY Ywhile the outgoing water passes over the other surface, to transfer the heat from the outgoing water to the ingoing water, and means for controlling the flow ofi outgoing water from the heat interchanger.

3. ln an apparatus of the character' described, the combination with the boiler7 of two pipes leading thereto and otherwise non-communicating, a source of fresh water supply connected with one pipe, the second 10 pipe being connected with the boiler at the desired water level, a feed pump and a measuring engine connected with the respective pipes7 and means connecting the engine and pump adapted to transmit the power delivered by the measuring engine to assist in driving the pump.

ln testimony of which invention, l have hereunto set my hand, at Philadelphia, Penna., on this 25th day of May, 1918.

FRANCIS I. DU PONT. 

